"They'd have to MITM SSL traffic largely."
To be fair, if anyone can do this it's precisely these people.
... still not likely, though, I agree.
Is that even possible if Google's SSL certs have Extended Validation? They'd have to have cooperation all the way down to the browser vendors and I can't see Mozilla caving that easily.
There are several governments (Spain, France, Netherlands, Japan) who publicly have Root CAs in the trusted browser list[1]. It seems pretty likely (cf say, Prism) that the NSA has a CA cert where they can generate whatever certificates they want in order to MITM browser SSL communications...
Can we remove Root CAs from our browser?
Edit: Found the answer: https://wiki.mozilla.org/CA:UserCertDB
Also, that's what they were doing for more traditional wiretaps and you should be sure that they have access to siphon off live traffic for analysis if they want.